1. Field of the Invention
The present invention generally relates to a facsimile image processing system. More specifically, the present invention is directed to an improvement in an MR (Modified READ) coding system for binary-coded images.
2. Description of the Related Art
Very recently, in facsimile apparatuses, the MR (modified READ) coding method regulated by C.C.I.T.T. (International Telegraph and Telephone Consulatative Commitee) has been usually employed as the method for coding binary-coded images.
Such an MR coding method is constructed of three typical modes, i.e., the pass mode, vertical mode and horizontal mode, and is operated in that the coding operation is sequentially carried out in combination with the positions of the respective color changing pixels on the coding line and the positions of the reference pixels either on the coding line, or immediately before this coding line.
FIG. 3 is a flowchart for showing the conventional two-dimensional coding operation by the MR coding system.
Assuming now such an image data as shown in FIG. 4a, when a pixel with a starting point "a0" is determined as shown in this figure, a detection is made at a step A3 to a first color changing pixel "a1" positioned at a right side of the starting point "a0" and also another detection is made at a step A4 to first and second color changing pixels "b1" and "b2" positioned at the right side of the starting point "a0" on a reference line in accordance with the conventional MR coding flow. Then, the process is advanced to a step A5 at which a check is made whether or not the second changing pixel "b2" is smaller than the first changing pixel "b1". In other words, a check is made whether "b2" is present at a right hand of "a1" or not. In this case, since the second changed pixel "b2" is positioned at a right hand of the first changing pixel "a1", this judgement result becomes "NO", and thereafter the process is advanced to a step A6 at which another check is made: .vertline.a1 b1.vertline..ltoreq.3. In this case, as the relative distance between "a1" and "b1" is equal to "3" and thus the judgement result becomes "YES", then the process is advanced to a step A7 whereby the coding operation is performed in the vertical mode. Then, the process is advanced to a step A8 at which the first changing pixel "a1" is set to the pixel "a0" with the starting point for the succeeding coding operation. Thereafter, the process is returned via the step A9 to the previous step A3, at which the changing pixels "a1", "b1" and "b2" are detected again so that the above-described operation is repeated.
In case that such an image data as shown in FIG. 4b is processed, a judgement is made at the step A5 whether or not the second changing pixel "b2" is smaller than the first changing pixel "a1". In this case, since the second changing pixel "b2" is positioned at a right side of the first changing pixel "a1", the judgement result becomes "NO" and the process is advanced to a step A6 at which another judgement is carried out whether or not .vertline.a1 b1.vertline..ltoreq.3. Since the relative distance between the first changing pixels "a1" and "b1" is longer than 3 and therefore the judgement result becomes NO, the process is advanced via steps A10 and A11 to a step A13, so that the coding operation is performed in the horizontal mode. Then, a changing pixel "a2" is set to a changing pixel "a0" for the subsequent coding operation at a step A14 and the process is advanced through a step A9 to the previous step A3, at which the above-described changing pixels "a1", "b1" and "b2" are newly and sequentially detected, whereby the above-described MR coding operation is repeated.
In accordance with the above-described conventional MR coding method or system, during the vertical mode represented in FIG. 4a, when the first changing pixel "a1" is set to a changing pixel "a0" for the next coding operation at the step A8, such a detection is performed as follows. That is to say, although the first changing pixel (b1) having the color opposite to that of the changing pixel (a0) positioned at the right hand with respect to the changing pixel (a0) on the first reference line, is the same as the previous changing pixel "b2", this first changing pixel (b1) is newly detected as (b1) at the subsequent step A4.
Also in the case when the changing pixel "a2" is set to the pixel (a0) for the subsequent coding operation in the horizontal mode shown in FIG. 4b, the following detecting operation is performed. Although both the first changing pixel (b1) having the color opposite to that of the changing pixel (a0) positioned at the right side of this changing pixel (a0) on the reference line, and also the first changing pixel (b2) positioned at the right side of the changing pixel (b1) on the reference line are the same as the previous changing pixels "b1" and "b2", these changing pixels "b1" and "b2" are newly detected as the pixels "b1" and "b2" at the subsequent step A4.
This implies that the previously checked changing points are again checked. As a result, a total number of detection process operations become very large for the changing points of the coding operation. Thus, large time consuming is required to detect such changing points, which impedes highspeed coding operations.